Soupsieve

- **NEW**: Update to support Python 3.12.
- **NEW**: Drop support for Python 3.7.

- **FIX**: Attribute syntax for case insensitive flag optionally allows a space, it does not require one.

- **NEW**: Update to support changes related to `:lang()` in the official CSS spec. `:lang("")` should match unspecified
languages, e.g. `lang=""`, but not `lang=und`.
- **NEW**: Only `:is()` and `:where()` should allow forgiving selector lists according to latest CSS (as far as Soup
Sieve supports "forgiving" which is limited to empty selectors).
- **NEW**: Formally drop Python 3.6.
- **NEW**: Formally declare support for Python 3.11.

- **FIX**: Documentation for installation from source is outdated.

- **FIX**: Fix some typos in error messages.

- **FIX**: Ensure attribute selectors match tags that have new lines characters in attributes. (233)